Innovative technologies for the design of a compact, low-cost, light-weight and inflatable space antenna are under development at a Southern California aerospace company as part of its partnership with a NASA technology demonstration program.

The technology will lead to the first large inflatable space antenna to be tested in orbit during a 1996 space shuttle mission.

Large space antennas many times the size of today's mechanical orbiting antennas are needed for a variety of applications in space, said Robert Freeland, manager of the antenna experiment at NASA's Jet Propulsion Laboratory. Among their many applications are spaceborne satellite antennas for mobile communications, Earth observations, active microwave sensing, astronomical observing and spacebased radar.

L'Garde Inc. of Tustin, Calif., is developing the technology for an orbital experiment that will take place in about a year and a half. NASA's Jet Propulsion Laboratory is facilitating development of the new technology, which was selected as one of many promising new technologies targeted for demonstration by NASA's In-Space Technology Experiments Program (IN-STEP).

Founded in 1986, IN-STEP makes testing of new technologies in space possible and speeds their transfer to the commercial sector. As facilitator of the new technology, JPL will also manage the on-orbit shuttle flight experiment.

The antenna experiment will be attached to a very small, recoverable spacecraft called the Spartan, which will be taken into orbit by one of NASA's space shuttles. Once on low-Earth orbit, the Spartan will provide a mounting platform for the antenna and its measurement system, power, attitude control and data recording. Deployment of the antenna structure will be monitored by two high-resolution television cameras on the experiment and on the space shuttle.

"The antenna is a 14-meter-diameter (46-foot) parabolic, or dish-shaped, reflector supported by an inflatable ring structure at its perimeter. Inflatable struts connect the reflector structure to the Spartan," Freeland said. "The reflector membrane will be made of aluminized mylar while the struts supporting the inflated dish will be made of Neoprene covered kevlar."

The facilities at L'Garde can accommodate the development of inflatable structures up to 14 meters in size at this time. However, demonstrations of hardware performance in this size range can be extrapolated up to 30meter (98-foot) structures, which are needed for applications such as Earth observations using radio waves and very long baseline interferometry.

The technology has been developed in a relatively short time frame and will be demonstrated for less than $10 million, which is a substantial savings over current, large size mechanical antennas costing close to $100 million or more to develop and deliver to space, Freeland said.

"A space structure of this size, weighing no more than 115 kilograms (250 pounds) for such a low cost is only possible because of the relative ease of designing, fabricating, testing and launching this class of structure," he said.

The experimental antenna will take about five minutes to deploy once the Spartan spacecraft has been positioned in low-Earth orbit. From there, a canister of nitrogen will be opened to pressurize the inflatable struts, torus and lenticular antenna reflector. Measurements of the parabolic mirror will then be taken to determine the surface accuracy and mechanical stability of the structure.

At the conclusion of the 90 minute experiment, the antenna will be separated from the Spartan spacecraft and allowed to fall back toward Earth, disintegrating as it travels through the atmosphere. The Spartan will then be grappled and recovered by the space shuttle's robotic arm as the shuttle passes by.

The In-Space Technology Experiments Program is sponsored by NASA's Office of Space Access and Technology, Washington, D.C.